1. Field of the Invention
The present invention generally relates to a weft insertion control apparatus in a jet loom. More particularly, the invention is concerned with a weft insertion control apparatus for a jet loom for controlling insertion of a weft into a warp shed under the action of air jet injected by a main weft inserting nozzle after the weft is released from a retaining action of a weft release stop mechanism capable of being changed over between a weft retaining state in which the weft is prevented from being drawn and a state in which the weft is released from the retained state.
2. Description of the Prior Art
For a jet loom, it is important for weaving a fabric of high quality to realize satisfactory conditions for insertion of a weft in which the leading end of the weft is caused to reach a weft arrival terminal position at a predetermined timing. As control factors or quantities which can affect the conditions for the weft insertion, there may be mentioned, for example, a weft insertion start timing at which the weft insertion commences and air jet injection timings of main and auxiliary weft inserting nozzles. In Japanese Unexamined Patent Application Publication No. 117853/62 (JP-A-62-117853), there is disclosed a weft insertion control mechanism which is so arranged as to compare an actual weft leading end arrival timing (i.e. time point at which the leading end of the weft reaches a predetermined goal or terminal position located widthwise of woven fabric) with a preset arrival timing to thereby control a weft release start timing of a weft retainer pin provided in association with a winding type weft length measuring/reserving device.
According to the prior art weft insertion control technique mentioned above, when the leading end of the weft as inserted has reached the predetermined goal position later than the preset time point, the weft insertion start timing is advanced correspondingly for a predetermined time, while the weft insertion timing is delayed correspondingly when the leading end of the inserted weft has reached the goal position earlier than the preset time point.
In this conjunction, it is however noted that there may occur three different states "normal", "late" and "early", respectively, for the weft leading end to reach a predetermined weft insertion goal position, being correspondingly accompanied with three different weft insertion start time points or timings. As a result, as many as nine different sets are conceived as combinations of weft insertion start conditions and weft leading end arrival conditions. Moreover, when taking into consideration the magnitudes or extents of deviations of the weft insertion start timing and the weft leading end arrival timing from the respective preset time points, there exist an enormous number of weft insertion conditions which can be identified discriminatively from one another. For this reason, it is impossible with the prior art simple weft insertion control technique to realize a fine weft insertion control in which numerous and various conditions or states for the weft insertion are properly taken into account.